1. Field of the Invention
The present invention relates to the field of agricultural implements for the preparation of soil for planting. More particularly, the invention pertains to a class of implements for delivering a substance or chemical into a discrete subsurface layer of the soil.
2. Description of the Prior Art
There are numerous references to agricultural implements for applying fertilizer, pesticides and fumigants to soil and crops.
A Spray Support Frame is shown in U.S. Pat. No. 3,874,593 issued to Wilt. The support frame has a plurality of arms mounted laterally thereon, the arms each having a generally downward facing nozzle affixed at its lower end for spraying the surface of the soil. The support frame may also carry soil cultivating and planting elements and suitable shoes or shovels for opening a fertilizer trench. No provision is made in the apparatus of Wilt for subsurface application.
U.S. Pat. No. 2,357,141 to Singleton discloses a Poison or Fertilizer Distributing Machine. In one version, a fertilizer distributing head is mounted laterally on a frame. The head contains a plurality of downward facing nozzles for delivering a fertilizer spray to the surface of the soil. Mounted rearwardly of the distributing heads is a plurality of cultivator shovels. Chemical application in Singleton is achieved by surface spraying followed by soil mixing, requiring the soil surface to be broken.
U.S. Pat. No. 2,881,848 to Liston for a Soil Treatment Applicator discloses an applicator for first applying ribbon-like bands of chemicals to the ground surface and then breaking up and submerging the chemically treated surface soil thereby intimately intermixing the chemically impregnated soil with the remainder of the top soil. As in Singleton, chemical application is achieved by surface application followed by soil mixing, no provision being made for direct subsurface application.
In U.S. Pat. No. 4,211,175 to Van der Lely an agricultural implement with soil penetrating tools and liquid spray booms is disclosed. The apparatus includes a set of sickle-shaped tines laterally disposed on a frame. Mounted behind the tines is a spray boom having a plurality of generally downward and rearward facing spray nozzles. The nozzles are laterally spaced so as to deliver a spray midway between the points where adjacent tines engaged the soil. Mounted to the rear of the spray nozzles are a pair of laterally extending rollers which act as cultivating members. Again, chemical application is through soil surface spraying, although the soil is first broken, and then sprayed, followed by a cultivating step.
U.S. Pat. No. 3,608,645 to Meiners for a Farm Trailer With Balancing Means recites "[a] bladed implement for dispensing the liquid fertilizer into the ground . . . ". The drawings in Meiners generally show a pair of blades or shovels having tubes attached to the aft faces thereof, the tubes leading from a chemical tank. Meiners does not further disclose details concerning the construction of this bladed instrument, nor the apparatus for injecting the fertilizer.
U.S. Pat. No. 4,683,826 to Solie et al. discloses a method of subsurface application of chemicals. The method includes the steps of: i) forcing a horizontally elongated implement through the soil at a depth sufficient to break up the subsurface of the soil without disturbing the surface; and ii) injecting chemicals in a jet substantially upward into the soil. The elongated implement is composed of a pair of trailing sweep wings angled to each other, and forming a pointed apex at the fore portion thereof. The sweep wings include a downwardly inclined plate-like element for disturbing a layer of soil under the surface. A manifold is laterally mounted to the wings, the manifold having a plurality of upwardly facing nozzles, evenly spaced from one another, for injecting a pressurized jet of chemical upward into the disturbed soil. The apparatus of the Solie patent can work at a depth of up to 8 centimeters.
Subsurface application of fumigants, pesticides and fertilizer is highly desirable. Subsurface application reduces the amount of the chemical that is lost through runoff and dissipation in the air. This means less of the chemical must be applied in the first place, which results not only in lower costs for application, but also provides environmental benefits. This is a significant factor in light of the public's concern for protection of water supplies and the farmer's need to continue production under an ever increasing regulatory scheme. Additionally, subsurface application goes to the root of the matter, so to speak, applying fertilizer and fumigants directly where they are need.
Proper subsurface application should take place 5 to 12 inches below the soil's surface. This has proven to be a problem until now, since it was believed that at least two levels of plates would be required to apply the chemical in a discrete layer at the proper depth. The additional layer of plates essentially doubled the drag, creating very large forces on all the parts of the applicator as well as the tractor used to pull the applicator. This made effective subsurface application virtually impossible.
It has long been believed that fumigants and the like only percolate downward into the soil. This required upward facing nozzles to properly distribute the chemical. Upward facing nozzles have presented a problem in the past, often becoming clogged.
Additionally, subsurface applicators have used a manifold having a relatively large number of nozzles. This increases manufacturing costs and complicates repair and maintenance. A simplified applicator structure is desirable to overcome these problems.